JP2005339817A - Abnormality detecting method of lighting device, and lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an abnormality detecting method of a lighting device as well as a lighting device capable stably detecting an abnormal fluorescent tube at end-of-life, even in a dimming state that the tube current flowing through the fluorescent tube is small and a difference of detected voltages between the abnormal fluorescent tube and a normal tube is small. <P>SOLUTION: A serial circuit of a current-limiting reactor L and a fluorescent tube K is connected between an output side of an inverter circuit composed of a direct current voltage Vi1, a drive circuit 10, a frequency control circuit 40, and transistors Tr1, Tr2, and a connecting point of capacitors C21, C2. A connecting point of the current-limiting reactor L and the fluorescent tube K is connected to a detecting circuit 20 to detect fluorescent tube voltage of the fluorescent tube K. At light adjustment, the frequency control circuit 40 temporarily lowers a switching frequency of the inverter circuit to measure the fluorescent tube voltage. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an illuminating device having an inverter circuit and a dimming function.

  In an illuminating device including an inverter circuit, a DC power source is converted into a high-frequency AC voltage by an inverter circuit and applied to a fluorescent tube, and the fluorescent tube is turned on at a high frequency. The fluorescent tube is composed of a glass tube coated with a fluorescent material and electrodes attached to both ends of the glass tube, and an emitter (electron emitting material) is coated on the electrode. When the fluorescent tube reaches the end of its life, it becomes a single emitterless state in which the emitter applied to the electrode on one side is lost. If the lighting operation is further continued in this one-emitter-less state, the filament will melt. If a voltage continues to be applied between filaments in a state where the filaments are blown (opened), there is a risk that a discharge will occur between the filaments and the glass in the fluorescent tube K will melt due to the temperature rise caused by this discharge. In particular, fluorescent tubes with high brightness and a thin tube diameter of 16 mm have recently been used. In this fluorescent tube having a tube diameter of 16 mm, there was a higher possibility that the glass of the fluorescent tube was melted due to the temperature rise caused by the discharge. For this reason, it is important to reliably detect the life of the fluorescent tube. Conventionally, methods for detecting the one-emitterless state of a fluorescent tube such as a fluorescent tube include a method for detecting the temperature of a switching element and a method for detecting the voltage of the fluorescent tube (fluorescent tube voltage). However, the method for detecting the temperature of the switching element has a problem that the detection speed is slow and the detection accuracy is poor. For this reason, a voltage detection method (for example, see Patent Document 1) with a relatively simple detection method is often used.

  An example of a conventional voltage detection method will be described with reference to FIG. FIG. 5 is a circuit diagram of a lighting device including a detection circuit 200 for detecting a fluorescent tube voltage. In addition to the detection circuit 200, a drive circuit for controlling and driving a DC power source Vi1, transistors Tr1, Tr2, and transistors Tr1, TR2. 10, current limiting reactor L, fluorescent tube K, capacitors C1 and C2, and preheating capacitor C3. A series circuit of transistors Tr1 and Tr2 and a series circuit of capacitors C1 and C2 are connected in parallel to the DC power source Vi1. A series circuit of a current-limiting reactor L and a fluorescent tube K is connected between a connection point between the transistors Tr1 and Tr2 and a connection point between the capacitors C1 and C2. A preheating capacitor C3 is connected to the fluorescent tube K. A connection point between the current-limiting reactor L and one electrode of the fluorescent tube K is connected to the detection circuit 200 and serves as an input unit that applies a fluorescent tube voltage to be detected by the detection circuit 200. The two transistors Tr1 and Tr2 are controlled so as to be alternately turned on and off by the drive circuit 10, and a high frequency voltage is applied to the fluorescent tube K to light the fluorescent tube K. Capacitors C1 and C2 cut direct current, and the capacitors C1 and C2 have the same capacitance value, and the other electrode of the fluorescent tube K is connected to the midpoint of both ends of the direct current power source Vi1 in an alternating manner.

The detection circuit 200 includes voltage dividing resistors R1 and R2 connected between the connection point A between the current limiting reactor L and one electrode of the fluorescent tube K and the negative electrode (reference potential) of the DC power source Vi1, and voltage dividing resistors. A diode D2 having an anode connected to a connection point B between the resistors R1 and R2 via a capacitor C4, a diode D1 having an anode connected to the reference potential and a cathode connected to a connection point C between the diode 2 and the capacitor C4, and a diode D2 The resistor R3 and the capacitor C5 are connected between the cathode and the reference potential, and the hysteresis comparator Cmp has the non-inverting input connected to the cathode of the diode 2 and the inverting input terminal connected to the reference voltage generating circuit Vref.
If the power supply voltage of the DC power supply Vi1 is 300 V, the voltage at the connection point A exceeds the power supply voltage range of the DC power supply Vi1, for example, −50 V to 350 V when the fluorescent tube K is turned on. The resistors R1 and R2 obtain a signal obtained by dividing this, and in the case of the above AC voltage of −50 V to 350 V, for example, the voltage is divided by about 1/50 and 3 V ± 4 V from the connection point B, and the amplitude is 8 V. Output a signal. The detection circuit 200 detects the entire amplitude of the signal including the voltage swinging to the minus side of the signal at the connection point B. The change range of the signal voltage at the connection point B is -V1 to V2 (V1, V2> 0). In a state where the potential at the connection point B is negative (compared to the reference potential) and is decreasing (increased in absolute value), the diode D2 is turned off (cut off), and the capacitor C4 is connected to the reference potential by the diode D1. And the capacitor C4 accumulates electric charge according to the difference between the reference potential and the potential of the connection point B, and the potential of the connection point C becomes equal to the reference potential (in order to simplify the description, the order of the diodes D1 and D2) Ignore the direction drop voltage). In this case, positive charges are accumulated on the electrode on the connection point C side of the capacitor C4. When the potential at the connection point B becomes the minimum potential −V1, the capacitor C4 stores −V1. Subsequently, when the potential at the connection point B starts to rise, the potential at the connection point C becomes positive (compared to the reference potential), and there is no charge injection through the diode D2. The operation during the period when the potential at the connection point B rises from -V1 to V2 is performed in the series circuit of the capacitors C3 and C4, with the capacitor C4 being charged with -V1 and the capacitor C5 being zero. The applied voltage changes from 0 to (V1 + V2). If the resistor R3 is ignored, when the potential at the junction B reaches the maximum value V2, the input voltage Vin to the non-inverting input terminal of the comparator Cmp is Vin = (V1 + V2) · C4 / (C4 + C5). The capacitance values of the capacitors C4 and C5 are also expressed as C4 and C5. Each time the signal B oscillates between -V1 and V2, the circuit is constituted by the capacitor C4 and the diodes D1 and D2, and charges are injected into the capacitor C5. The voltage Vin is determined where the discharge of the capacitor C5 by the resistor R3 balances. This voltage Vin gives an indication of the total amplitude (V1 + V2) of the signal B, ie the fluorescent tube voltage. The hysteresis comparator Cmp compares the signal Vin with the output voltage Vref from the reference voltage generation circuit Vref, and outputs H (high level) as the output signal Vout when it is determined that Vin> Vref. In Patent Document 1, since the fluorescent tube voltage rises as compared with the normal state at the end of life, it is determined that the end of life of the fluorescent tube is reached when H is continuously output as Vout.
JP 05-062785 (page 3-4, FIG. 1)

  Some illuminating devices control the switching frequency of the transistors Tr1 and Tr2 and the voltage value of the DC power supply of the inverter to increase or decrease the tube current flowing through the fluorescent tube, thereby adjusting the light. An example of the configuration is shown in FIG. The circuit shown in FIG. 6 differs from the circuit shown in FIG. 5 in that the DC power source Vi1 is changed to a variable voltage type DC power source Vi2, and the output voltage of the DC power source Vi2 and the switching frequency of the transistors Tr1 and Tr2 are controlled. 30 is provided. Dimming is performed by reducing the light emission of the fluorescent tube by reducing the tube current of the fluorescent tube relative to the normal time. The principle of dimming with the switching frequency is as follows. In other words, the fluorescent tube after lighting has the same characteristics as a normal resistor, and together with the current-limiting reactor L and the capacitors C1 and C2, configures the load of the LCR for the inverter output output from the connection point of the transistors Tr1 and Tr2. To do. Normally, since the operation is performed at a frequency higher than the resonance frequency of the LCR circuit, the current is decreased and darkened when the frequency is increased, and the current is increased and brightened when the frequency is decreased.

According to the knowledge obtained by the applicant's research and development, the dimming function, that is, the fluorescent tube voltage characteristics of the normal fluorescent tube and the abnormal fluorescent tube at the end of life with respect to the tube current are as shown in FIG. In FIG. 7, the horizontal axis represents the tube current, and the larger the value, the brighter the fluorescent tube. The vertical axis represents the detection voltage (corresponding to the above-mentioned Vin) detected by the detection circuit 200. As can be seen from FIG. 7, when the fluorescent tube is operating at the maximum output, there is a large difference in detection voltage between the abnormal fluorescent tube and the normal fluorescent tube, and there is no problem in detecting the fluorescent tube abnormality. However, as the light is dimmed by reducing the tube current flowing through the fluorescent tube and darkening the light emission, the difference in detection voltage between the abnormal fluorescent tube and the normal fluorescent tube becomes smaller, and the abnormality is detected by the conventional abnormality detection method. The problem arises that it becomes difficult.
The present invention has been made in view of the above points. The object of the present invention is to solve the above-mentioned problems and stably detect abnormal fluorescent tubes at the end of life even in a dimming state with a small tube current. An object of the present invention is to provide a lighting device abnormality detection method and a lighting device.

Therefore, in order to solve the above-mentioned problem, the invention according to claim 1 is directed to a discharge lamp, an inverter circuit that converts a DC voltage to a reactor connected in series with the discharge lamp and supplies an AC voltage, and the AC voltage. In a lighting device having a dimming function for controlling the brightness of the discharge lamp by changing the frequency of the discharge lamp or changing the DC voltage, the frequency of the AC voltage is lowered when the discharge lamp is dimmed. This is an abnormality detection method for an illumination device that detects an abnormality of the discharge lamp by detecting a potential at a connection portion between the discharge lamp and the reactor.
According to a second aspect of the present invention, there is provided a discharge lamp and an inverter circuit that converts a DC voltage to a reactor connected in series to the discharge lamp to supply an AC voltage, and changes the frequency of the AC voltage or the DC voltage In a lighting device having a dimming function for controlling the brightness of the discharge lamp by changing the voltage, the voltage value of the DC voltage is increased when the discharge lamp is dimmed to connect the discharge lamp and the reactor. It is the abnormality detection method of the illuminating device which detects abnormality of the said discharge lamp by detecting the electric potential.

According to a third aspect of the present invention, there is provided a discharge lamp, an inverter circuit for supplying an alternating voltage by converting a direct current voltage to a reactor connected in series to the discharge lamp, and changing the frequency of the alternating voltage or the direct current voltage. In a lighting device having a dimming function for controlling the brightness of the discharge lamp by changing the frequency control, the frequency of the AC voltage is temporarily lowered when the discharge lamp is dimmed during an abnormality detection operation. It is an illuminating device provided with the detection circuit which detects the abnormality of the said discharge lamp by detecting the electric potential of the connection part of a circuit and the said discharge lamp and a reactor.
According to a fourth aspect of the present invention, there is provided a discharge lamp, an inverter circuit for supplying an alternating voltage by converting a direct current voltage to a reactor connected in series to the discharge lamp, and a frequency of the alternating voltage or changing the direct current voltage. In a lighting device having a dimming function for controlling the brightness of the discharge lamp by changing, a power supply that temporarily increases the voltage value of the DC voltage when the discharge lamp is dimmed during an abnormality detection operation It is an illuminating device provided with the detection circuit which detects the abnormality of the said discharge lamp by detecting the electric potential of the connection part of a control circuit and the said discharge lamp and a reactor.

    The abnormality detection method for an illumination device and the illumination device according to the present invention provide a frequency or voltage even if the illumination device is operated in a dimming state where the difference between the fluorescent tube voltage of the abnormal fluorescent tube and the fluorescent tube voltage of the normal fluorescent tube is small. Since the fluorescent tube voltage is measured after temporarily increasing the fluorescent tube current to make a difference in the fluorescent tube voltage easy to change, it is possible to detect abnormal fluorescent tubes stably even during dimming it can. In addition, since the time for increasing the fluorescent tube current is limited, flicker does not occur in the fluorescent lamp.

  Here, as an embodiment of the present invention, if the tube current is increased when the tube current is increased, even if the difference between the fluorescent tube voltage of the abnormal fluorescent tube and the fluorescent tube voltage of the normal fluorescent tube is small when the tube current during dimming is small, Focusing on the fact that the difference in the tube voltage can be increased, a case where the tube current is temporarily increased when detecting the fluorescent tube voltage during dimming will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing a first embodiment of the present invention. The same components as those in FIG. The specific configuration of the detection circuit 20 may be the same as that of the detection circuit 200 of FIG. 5, but is not limited to this, and any configuration having an equivalent function may be used. The transistors Tr1 and Tr2 may be MOSFETs or bipolar transistors, but FIG. 1 shows an example in which MOSFETs are applied.
The lighting circuit of FIG. 1 controls the brightness of the fluorescent tube by the operating frequency (switching frequency) of the inverter. The frequency control circuit 40 controls the operating frequency of the inverter in the dimming control, and also controls the operating frequency when measuring the fluorescent tube voltage. According to the knowledge obtained by the present applicant as in FIG. 7, the fluorescent tube voltage characteristics of the normal fluorescent tube and the abnormal fluorescent tube at the end of life with respect to the operating frequency of the inverter are as shown in FIG. As described above, the fluorescent tube is dark when the operating frequency is high, and bright when the operating frequency is low. In the case where the fluorescent tube voltage is measured when the fluorescent tube is operating at the frequency f1 in FIG. 2, that is, the dimming is performed so as to suppress the light emission amount of the fluorescent tube, in this embodiment, frequency control is performed prior to the measurement. The circuit 40 temporarily changes the operating frequency to f2, and controls the driving circuit 10 to return the operating frequency to f1 after the measurement is completed. In the conventional lighting device, the fluorescent tube voltage is measured with the operating frequency f1, but the difference in detection voltage between the abnormal fluorescent tube and the normal fluorescent tube is small as shown in FIG. 2, making it difficult to detect the abnormal fluorescent tube. . At the operating frequency f2, as shown in FIG. 2, the difference in detection voltage between the abnormal fluorescent tube and the normal fluorescent tube is sufficiently large, and there is no problem in detecting the abnormal fluorescent tube. In this embodiment, when the fluorescent tube voltage is measured, the operating frequency is temporarily changed from f1 to f2, so that the abnormal fluorescent tube can be reliably detected. The operating frequency f2 at the time of measurement is set between the dimming operating frequency f1 and the maximum output operating frequency f3 (f1> f2 ≧ f3).

  When in the dimming state f1, the operation frequency is controlled to be set to f2 at regular intervals. The interval at which the operating frequency is set to f2 is 1 Hz or less, or about 200 Hz or more, and the operation time at f2 is 0.1 s (seconds) or the duty is set to about 10% or less, so that the fluorescent tube No flickering occurs.

A second embodiment of the present invention is shown in FIG. The same components as those in FIG.
In the illumination circuit of FIG. 3, the brightness of the fluorescent tube is controlled by the voltage of the DC power supply Vi2 of the inverter. The voltage control circuit 50 controls the output voltage of the DC power supply Vi2 of the inverter in the dimming control, and also controls the output voltage when measuring the fluorescent tube voltage. According to the knowledge obtained by the present applicant as in FIGS. 2 and 7, the fluorescent tube voltage characteristics of the normal fluorescent tube and the abnormal fluorescent tube at the end of life with respect to the output voltage of the DC power source Vi2 are as shown in FIG. The fluorescent tube is controlled to be bright when the power supply voltage is high and dark when it is low. When measuring the fluorescent tube voltage when the fluorescent tube is operating in the state of the voltage V1 in FIG. 2, that is, when the fluorescent tube is dimmed to suppress the amount of light emitted from the fluorescent tube, in this embodiment, voltage control is performed prior to the measurement. The circuit 50 temporarily changes the power supply voltage to V2, and controls the DC power supply circuit Vi2 to return the power supply voltage to V1 after the measurement is completed. In the conventional lighting device, the fluorescent tube voltage is measured while the power supply voltage is V1, but as shown in FIG. 4, the difference in detection voltage between the abnormal fluorescent tube and the normal fluorescent tube is small, and it is difficult to detect the abnormal fluorescent tube. . In the power supply voltage V2, as shown in FIG. 4, the difference in detection voltage between the abnormal fluorescent tube and the normal fluorescent tube is sufficiently large, and there is no problem in detecting the abnormal fluorescent tube. In this embodiment, when the fluorescent tube voltage is measured, the power supply voltage is temporarily changed from V1 to V2, so that the abnormal fluorescent tube can be reliably detected. The power supply voltage at the time of measurement is set between the power supply voltage V1 at the time of dimming and the power supply voltage V3 that is the maximum output (V1 ≧ V2> V1).

When in the dimming state V1, the power supply voltage is controlled to be set to V2 at regular intervals. The interval for setting the power supply voltage to V2 is 1 Hz or less, or about 200 Hz or more, and the operation time at V2 is set to 0.1 s (seconds) or the duty is set to about 10% or less. No flickering occurs.
In the first embodiment, the fluorescent tube voltage measurement in the lighting device that controls the dimming control at the operating frequency is supported by changing the operating frequency. In the second embodiment, the fluorescent tube in the lighting device that performs the dimming control by the power supply voltage of the inverter. The voltage measurement was supported by changing the inverter power supply voltage, but it is not limited to this combination. For the fluorescent tube voltage measurement in the lighting device that controls the dimming control at the operating frequency, the inverter power supply voltage may be changed, or for the fluorescent tube voltage measurement in the lighting device that performs the dimming control by the inverter power supply voltage. On the other hand, the operation frequency may be changed.

It is a circuit diagram for demonstrating Example 1 of this invention. It is a graph which shows the relationship between an operating frequency and a detection voltage. It is a circuit diagram for demonstrating Example 2 of this invention. It is a graph which shows the relationship between a power supply voltage and a detection voltage. It is a circuit diagram for demonstrating the conventional illuminating device and the detection circuit of a fluorescent tube voltage. It is a circuit diagram for demonstrating the conventional illuminating device with a light control function. It is a graph which shows the relationship between the tube current which flows into a fluorescent tube, and a detection voltage.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Drive circuit 20,200 Detection circuit 30 Control circuit 40 Frequency control circuit 50 Voltage control circuit Cmp Hysteresis comparator C1-C5 Capacitor D1, D2 Diode K Fluorescent tube L Current-limiting reactor Tr1, Tr2 Transistor Vi1, Vi2 DC power supply Vref Reference voltage generation Circuit (and its output voltage)

Claims (4)

A discharge lamp and an inverter circuit for converting a DC voltage to a reactor connected in series to the discharge lamp and supplying an AC voltage; and changing the frequency of the AC voltage or changing the DC voltage In a lighting device having a dimming function for controlling brightness, when the discharge lamp is dimmed, the frequency of the AC voltage is lowered to detect the potential of the connection portion between the discharge lamp and the reactor. An abnormality detection method for an illumination device, characterized by detecting an abnormality in an electric lamp. A discharge lamp and an inverter circuit for converting a DC voltage to a reactor connected in series to the discharge lamp and supplying an AC voltage; and changing the frequency of the AC voltage or changing the DC voltage In a lighting device having a dimming function for controlling brightness, when the discharge lamp is dimmed, the voltage value of the DC voltage is increased to detect the potential of the connection portion of the discharge lamp and the reactor. An abnormality detection method for an illumination device, characterized by detecting an abnormality in a discharge lamp. A discharge lamp and an inverter circuit for converting a DC voltage to a reactor connected in series to the discharge lamp and supplying an AC voltage; and changing the frequency of the AC voltage or changing the DC voltage In a lighting device having a dimming function for controlling brightness, when the discharge lamp is dimmed during an abnormality detection operation, a frequency control circuit that temporarily lowers the frequency of the AC voltage and the discharge lamp and the reactor An illumination apparatus comprising: a detection circuit that detects an abnormality of the discharge lamp by detecting a potential of a connection portion. A discharge lamp and an inverter circuit for converting a DC voltage to a reactor connected in series to the discharge lamp and supplying an AC voltage; and changing the frequency of the AC voltage or changing the DC voltage In a lighting device having a dimming function for controlling brightness, when the discharge lamp is dimmed during an abnormality detection operation, a power supply control circuit for temporarily increasing the voltage value of the DC voltage, and the discharge lamp and the reactor An illuminating device comprising: a detection circuit that detects an abnormality of the discharge lamp by detecting a potential of the connection portion.

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